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Turkish police secure the area outside the Ankara art gallery where the Russian Ambassador to Turkey Andrei Karlov was shot dead, Dec. 19, 2016, in Ankara. Getty Images

The Russian Ambassador to Turkey was shot dead Monday as he spoke at an Ankara art exhibition, one day before prominent Syria peace talks were set to take place between the foreign and defense ministers of Russia, Turkey and Iran.

Ambassador Andrei Karlov was a few minutes into his speech at the event, which was attended by a number of press photographers, when the diplomat was shot multiple times in the back, fatally wounding him. Three others were reportedly injured by gunfire, as well. The assailant, identified as an off-duty Turkish police officer Mert Altintas, could be seen wearing a black suit and tie and apparently used his police credentials to enter the event and stand behind the ambassador, waiting to strike.

After shooting the diplomat, Altintas reportedly spoke in Turkish and referenced the conflict in Syria. He yelled "Don't forget Aleppo!", the city of which the Syrian army — supported by Russian airpower and Iran-backed paramilitary ground forces — recently regained control, dealing a major defeat to Western and Turkey-sponsored rebels. Altintas is also quoted as saying "Allahu Akbar," or "God is great," in Arabic before opening fire on the diplomat, killing him. Turkish and Russian officials have pointed toward a possible Islamist inspiration for the assassination, which both have called it a terrorist attack and a "provocation."

As the events unfolded, a number of amateur and professional photographers such as AP's Burhan Ozbilici in the audience continued to operate their cameras, recording the attack in real time. These graphic images and videos have been shared across the internet. They capture the diplomat's last moments as well as the gunman's impassioned rant and bloody demise.

Some on social media have suggested the potential historic value of the images and drawn comparisons to the assassination of Archduke Franz Ferdinand of Austria, who was gunned down in 1914 by Gavrilo Princip, a Bosnian Serb, Yugoslav nationalist and member of a secret society known as the Black Hand. Ferdinand's killing is often regarded as one of the leading catalysts that sparked World War One.

The following video footage and photographs are graphic in nature. Please view them at your own discretion.